// Basic Pingy example for Nodate framework.
// This uses the same API calls as with the Arduino framework.

#include <Arduino.h>

const int pingPin = 7;

long microsecondsToInches(long microseconds);

long microsecondsToCentimeters(long microseconds);

int main () {
	// Initialise.
	init(); // for wiring.h
	initVariant();

    // establish variables for duration of the ping, and the distance result
    // in inches and centimeters:
    long duration, inches, cm;

    // The PING))) is triggered by a HIGH pulse of 2 or more microseconds.
    // Give a short LOW pulse beforehand to ensure a clean HIGH pulse:
    pinMode(pingPin, OUTPUT);
    digitalWrite(pingPin, LOW);
    delayMicroseconds(2);
    digitalWrite(pingPin, HIGH);
    delayMicroseconds(5);
    digitalWrite(pingPin, LOW);

    // The same pin is used to read the signal from the PING))): a HIGH pulse
    // whose duration is the time (in microseconds) from the sending of the ping
    // to the reception of its echo off of an object.
    pinMode(pingPin, INPUT);
    duration = pulseIn(pingPin, HIGH);

    // convert the time into a distance
    inches = microsecondsToInches(duration);
    cm = microsecondsToCentimeters(duration);

    Serial.print(inches);
    Serial.print("in, ");
    Serial.print(cm);
    Serial.print("cm");
    Serial.println();

    delay(100);
}

long microsecondsToInches(long microseconds) {
    // According to Parallax's datasheet for the PING))), there are 73.746
    // microseconds per inch (i.e. sound travels at 1130 feet per second).
    // This gives the distance travelled by the ping, outbound and return,
    // so we divide by 2 to get the distance of the obstacle.
    // See: http://www.parallax.com/dl/docs/prod/acc/28015-PING-v1.3.pdf
    return microseconds / 74 / 2;
}

long microsecondsToCentimeters(long microseconds) {
    // The speed of sound is 340 m/s or 29 microseconds per centimeter.
    // The ping travels out and back, so to find the distance of the object we
    // take half of the distance travelled.
    return microseconds / 29 / 2;
}

